1. Field of the Invention
The present invention relates to an ultrasound probe which performs transmission and reception of ultrasonic waves, and to an ultrasound diagnostic apparatus which performs transmission and reception of ultrasonic waves to produce an ultrasound image.
2. Description of the Related Art
An ultrasound diagnostic apparatus using an ultrasound image has hitherto been put into practical use in the field of medicine. In general, this kind of ultrasound diagnostic apparatus has an ultrasound probe embedded with a transducer array and an ultrasound diagnostic apparatus body connected to the ultrasound probe. An ultrasonic wave is transmitted from the ultrasound probe toward a subject, an ultrasonic echo signal from the subject is received by the ultrasound probe, and the reception signal is electrically processed in the ultrasound diagnostic apparatus body to produce an ultrasound image.
In recent years, in order to improve convenience of an operator, such as a technician, the provision of various switches has been considered in the ultrasound probe to control the operation of the ultrasound diagnostic apparatus. For example, JP 2004-248973 A describes a technique in which an imaging plane is appropriately switched by a selection switch provided in a hand grip of the ultrasound probe without touching the ultrasound diagnostic apparatus body.
In general, the ultrasound probe uses a piezoelectric device as an ultrasound transducer which transmits and receives an ultrasonic wave. When transmitting an ultrasonic wave, an activation signal having a large amount of energy is supplied to the ultrasound transducer. However, the entire amount of energy of the activation signal is not converted to ultrasonic energy in the ultrasound transducer, and some amount of energy is converted to heat. For this reason, the ultrasound transducer generates heat. In a transmission/reception control circuit which is used for transmission and reception of an ultrasonic wave by the ultrasound transducer, the activation signal is converted to heat. Accordingly, when transmission of an ultrasonic wave is performed by the ultrasound transducer, the entire ultrasound probe increases in temperature. Since the ultrasound probe is used in a state of being in contact with a biological body, such as a human body, from the viewpoint of low-temperature burn prevention or the like, the surface temperature is limited and should be equal to or lower than 43° C.
In the ultrasound diagnostic apparatus which is usually used for medical treatment or medical examination in a hospital, the ultrasound diagnostic apparatus body and the ultrasound probe are connected through a cable. In recent years, in order to remove the burden of the cable and to improve convenience of the operator, in particular, in a portable ultrasound diagnostic apparatus which is usable outside, such as a disaster area, not inside, such as a hospital, a wireless probe has been developed in which wireless communication is performed between the ultrasound diagnostic apparatus body and the ultrasound probe. The wireless probe should be provided with various circuits for wireless communication therein along with the ultrasound transducer. Accordingly, in the wireless probe, heat is more likely to be generated compared to a general ultrasound probe with cable connection.
In order to prevent heat generation of the ultrasound probe, an increase in the surface area of the ultrasound probe or the provision of a cooling mechanism in the ultrasound probe has been considered. However, it is preferable that the ultrasound probe is of small size. The smaller the size of the ultrasound probe, the smaller the surface area. For this reason, there is a problem in that the heat dissipation area decreases, and the ability to radiate heat generated from the ultrasound transducer or an internal circuit is insufficient. There is also a problem in that, as the ultrasound probe is of small size, it is difficult to secure the space where the cooling mechanism is mounted.
As another method which prevents heat generation of the ultrasound probe, suppression of power consumption in the ultrasound probe has been considered. JP 2005-253776 A describes an ultrasound diagnostic apparatus which automatically changes the activation condition of the ultrasound transducer in accordance with the surface temperature of the ultrasound probe so as to prevent the surface of the ultrasound probe from reaching at high temperature.
On the other hand, in the apparatus described in JP 2004-248973 A, when a puncture guideline at the time of insertion of a puncture needle is displayed, even if the operator unintentionally touches the switch of the ultrasound probe, the operation of the switch of the ultrasound probe is limited such that an imaging plane where the image of the puncture needle is detectable is not switched to another imaging plane where the image of the puncture needle is not viewed. In this case, there is a problem in that heat generation in the ultrasound transducer, the transmission/reception control circuit, or the like, in particular, heat generation in the wireless probe is not taken into consideration.
In the apparatus described in JP 2005-253776 A, the value, such as a frame rate, is primarily determined in accordance with the surface temperature of the ultrasound probe, or the like. Accordingly, there is a problem in that a desirable ultrasound image for the operator may not be obtained.